Method and device for subband coding frequency conversion unit, and method and device for image encoding/decoding using same

ABSTRACT

A method performed by an apparatus for decoding a video, includes: generating a predicted block by predicting a current block to be decoded; reconstructing frequency coefficients in a frequency conversion unit by decoding a bitstream, to generate a frequency conversion block having a size of the frequency conversion unit; inversely transforming the frequency conversion block by using a transform size identical to the size of the frequency conversion unit, to reconstruct a residual block; and adding the reconstructed residual block to the predicted block.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/811,581 filed Apr. 10, 2013, which is a the National Phaseapplication of International Application No. PCT/KR2011/004906, filedJul. 5, 2011, which is based upon and claims the benefit of prioritiesfrom Korean Patent Application No. 10-2010-0069663, filed on Jul. 19,2010. The disclosures of the above-listed applications are herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates in some embodiments to a method and anapparatus for subband-coding a frequency conversion unit, and a methodand an apparatus for video encoding/decoding using the same.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and do not constitute prior art.

Moving Picture Experts Group (MPEG) and Video Coding Experts Group(VCEG) together stepped ahead of the existing MPEG-4 Part 2 and H.263standard methods to develop a better and more excellent videocompression technology. The standard is called H.264/AVC (Advanced VideoCoding) and was released simultaneously as MPEG-4 Part 10 AVC and ITU-TRecommendation H.264.

H.264/AVC (hereinafter referred to as ‘H.264’) standard performs anintra and/or inter prediction process by the unit of macroblock havingdifferent shapes of subblocks to generate a residual signal. A 4×4pixels subblock level frequency conversion unit of the generatedresidual signal is then encoded through processes including a frequencytransform, quantization, entropy encoding.

Recent video compression technologies are under development to meet thedemand for ultra high resolution videos, and the international standardorganizations of MPEG and VCEG are jointly developing an HEVC videoencoding standard by the name of JCT. The inventor(s) has noted that,other than typical 4×4 pixels and 8×8 pixels frequency units often usedin known video compression technologies, larger frequency conversionunits such as 16×16 pixels are of great help to improve the videocompression efficiency. However, the inventor(s) has experienced asingle complete scanning over such a 16×16 block by the known methodcauses difficulty in devising and implementing an efficient frequencycoefficient encoding method and apparatus depending on the videocharacteristics.

SUMMARY

In accordance with some embodiments of the present disclosure, a methodperformed by an apparatus for decoding a video, comprise: generating apredicted block by predicting a current block to be decoded;reconstructing frequency coefficients in a frequency conversion unit bydecoding a bitstream, to generate a frequency conversion block having asize of the frequency conversion unit; inversely transforming thefrequency conversion block by using a transform size identical to thesize of the frequency conversion unit, to reconstruct a residual block;and adding the reconstructed residual block to the predicted block.Herein, the reconstructing of the frequency coefficients comprises:identifying a plurality of subblocks in the frequency conversion unit;decoding, from the bitstream, information indicating whether a subblockin the frequency conversion unit has at least one non-zero frequencycoefficient; reconstructing frequency coefficients in the subblock fromthe bitstream, when the information indicates that the subblock has atleast one non-zero frequency coefficient; and setting all frequencycoefficients in the subblock to 0, when the information indicates thatthe subblock does not have at least one non-zero frequency coefficient.

In accordance with some embodiments of the present disclosure, a videodecoding apparatus comprises a decoder, an inverse transformer, apredictor and an adder. The decoder is configured to reconstructfrequency coefficients in a frequency conversion unit by decoding abitstream, and generate a frequency conversion block having a size ofthe frequency conversion unit. The inverse transformer is configured toinversely transform the frequency conversion block by using a transformsize identical to the size of the frequency conversion unit, toreconstruct a residual block. The predictor is configured to generate apredicted block by predicting a current block to be decoded. And theadder is configured to add the reconstructed residual block to thepredicted block. Herein, the decoder is configured to identify aplurality of subblocks in the frequency conversion unit, decode, fromthe bitstream, information indicating whether a subblock in thefrequency conversion unit has at least one non-zero frequencycoefficient, reconstruct frequency coefficients in the subblock from thebitstream, when the information indicates that the subblock has at leastone non-zero frequency coefficient, and set all frequency coefficientsin the subblock to 0, when the information indicates that the subblockdoes not have at least one non-zero frequency coefficient.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram schematically of a video encodingapparatus according to at least one embodiment of the presentdisclosure;

FIG. 2 is a block diagram of an apparatus 200 for subband-coding afrequency conversion unit according to at least one embodiment of thepresent disclosure;

FIGS. 3A to 3F illustrate various examples of splitting the frequencyconversion unit into a plurality of frequency domains, and FIG. 4illustrates numbers of frequency domains when a 16×16 frequencyconversion unit is split into four 8×8 frequency domains;

FIG. 5 is an example schematized from parallel scan operations of afrequency domain scan unit 230;

FIG. 6 is a schematic block diagram of a configuration of a videodecoding apparatus according to at least one embodiment of the presentdisclosure; and

FIG. 7 is a flowchart of a method of subband-coding a frequencyconversion unit.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In the followingdescription, the same elements will be designated by the same referencenumerals although they are shown in different drawings. Further, in thefollowing description of the present disclosure, a detailed descriptionof known functions and configurations incorporated herein will beomitted when it may make the subject matter of the present disclosurerather unclear.

Additionally, in describing the components of the present disclosure,there may be terms used like first, second, A, B, (a), and (b). Theseare solely for the purpose of differentiating one component from theother but not to imply or suggest the substances, order or sequence ofthe components. If a component were described as ‘connected’, ‘coupled’,or ‘linked’ to another component, they may mean the components are notonly directly ‘connected’, ‘coupled’, or ‘linked’ but also areindirectly ‘connected’, ‘coupled’, or ‘linked’ via a third component.

Hereinafter, a video encoding apparatus, a video decoding apparatus, andan apparatus for subband-coding a frequency conversion unit describedbelow may be user terminals such as a Personal Computer (PC), a notebookcomputer, a Personal Digital Assistant (PDA), a Portable MultimediaPlayer (PDA), a PlayStation Portable (PSP), a wireless communicationterminal, a smart phone and the like, or server terminals such as anapplication server, a service server and the like, and may refer tovarious apparatuses including a communication apparatus such as acommunication modem and the like for performing communication withvarious types of devices or a wired/wireless communication network, amemory for storing various types of programs and data for encoding ordecoding a video, or performing an inter or intra prediction for theencoding or decoding, and a microprocessor and the like for executingthe program to perform an operation and a control.

Further, a video encoded into a bitstream by the video encodingapparatus is transmitted in real time or non-real-time to the videodecoding apparatus through wired/wireless communication networks such asan Internet, a short distance wireless communication network, a WiBro(aka WiMax) network, a mobile communication network and the like orthrough various communication interfaces such as a cable, a UniversalSerial Bus (USB) and the like, and thus decoded in the video decodingapparatus and reconstructed and reproduced as the video.

A video typically may include a series of pictures each of which issplit into predetermined domains, such as frames or blocks. When thedomain of the video is split into blocks, the split blocks may beclassified into an intra block or an inter block depending on anencoding method. The intra block means a block that is encoded throughan intra prediction coding method which generates a predicted block bypredicting a pixel of a current block using pixels of a reconstructedblock that underwent previous encoding and decoding and then encodes adifferential value between the predicted block and the pixel of thecurrent block within a current picture where the current encoding isperformed. The inter block means a block that is encoded through aninter prediction encoding which generates the predicted block bypredicting the current block in the current picture through referencingone or more past pictures or future pictures and then encoding thedifferential value of the predicted block from the current block. Here,the picture that is referenced in encoding or decoding the currentpicture is called a reference picture.

Some embodiments of the present disclosure provide a method and anapparatus for subband-coding the frequency conversion unit, and a methodand an apparatus for video encoding and/or decoding using the samewherein the frequency conversion unit is split into at least onefrequency domain so that frequency domain encoding information isencoded to indicate the possible existence of a non-zero frequencycoefficient in each frequency domain, and thereby enhance the videocompression efficiency.

FIG. 1 is a schematic block diagram of a video encoding apparatusaccording to at least one embodiment of the present disclosure.

A video encoding apparatus 100 includes a predictor 110 or 120, asubtractor 130, a transformer and quantizer 140, an encoder 150, aninverse quantizer and inverse transformer 160, an adder 170, and a framememory 180. Other components of the video encoding apparatus 100, suchas the predictor 110 or 120, the subtractor 130, the transformer andquantizer 140, the encoder 150, the inverse quantizer and inversetransformer 160, the adder 170 are each implemented by one or moreprocessors and/or application-specific integrated circuits (ASICs). Theframe memory 180 includes at least one non-transitory computer readablemedium. The video encoding apparatus 100 includes input components(e.g., a keyboard, a mic, a touch pad, and so on) and output components(e.g., such as a speaker, a display screen, a printer and so on).

An input video to be encoded is input by the unit of macroblock. Themacroblock has an M×N type (i.e., M×N pixels type), and M and N have asize of 2^(n), respectively, or M and N may be the same as or differentfrom each other in the present disclosure. Accordingly, the macroblockin the present disclosure may be the same as or larger than themacroblock in the H.264 standard.

The predictor 110 or 120 predicts a current block to generate apredicted block. That is, the predictor 110 or 120 predicts a pixelvalue of each pixel of the current block to be encoded in the video togenerate the predicted block having the predicted pixel value of eachpixel. Here, the predictor 110 or 120 can predict the current block byusing an intra prediction by the intra predictor 110 or an interprediction by the inter predictor 120.

The intra predictor 110 generates the predicted block by using adjacentpixels in order to predict a current macroblock. That is, the intrapredictor 110 generates the predicted block according to a mode of theintra predictor 110 by using the adjacent pixels of the currentmacroblock which have been already reconstructed through an encodingprocess.

The inter predictor 120 generates the predicted block by using adifferent frame in order to predict the current macroblock. That is, theinter predictor 120 generates a motion vector through a motionestimation according to a mode of the inter predictor 120 in a previousframe which has been already reconstructed through an encoding process,and generates the predicted block in a motion compensation process usingthe motion vector.

The subtractor 130 subtracts the predicted block from the current blockto generate a residual block. That is, the subtractor 130 calculates adifference between the pixel value of each pixel of the current block tobe encoded and a pixel value of the predicted block generated by theintra predictor 110 or the inter predictor 120 to generate the residualblock having a residual signal in a block type.

The transformer and quantizer 140 transforms and quantizes the residualblock generated by the subtractor 130 to a frequency coefficient. Here,a transform method may use a technique for converting a video signal ofa spatial domain to a video signal of a frequency domain such as aHadamard transform, or a discrete cosine transform based integertransform (hereinafter, referred to as an “integer transform”), and aquantization method may use various quantization techniques such as aDead Zone Uniform Threshold Quantization (hereinafter, referred to as a“DZUTQ”) or a quantization weighted matrix.

The encoder 150 encodes the residual block transformed and quantized bythe transformer and quantizer 140 to generate encoded data.

Such an encoding technology may include an entropy encoding technology,but is not limited thereto and may include various different encodingtechnologies.

Further, the encoder 150 may insert various information required fordecoding the encoded bitstream as well as the bitstream encoded fromquantization frequency coefficients in the encoded data. That is, theencoded data may include a first field containing a Coded Block Pattern(CBP), and a bitstream encoded from a delta quantization coefficient (orparameter) and the quantization frequency coefficient, and a secondfield containing a bit for information required for the prediction (forexample, an intra prediction mode in the intra prediction, the motionvector in the inter prediction or the like).

Unlike the H.264 standard, when the encoder 150 encodes the residualblock of the quantized frequency coefficient in the embodiment of thepresent disclosure, the encoder 150 splits a frequency conversion unitof the residual block (that is, frequency conversion block) of thequantized frequency coefficient into one or more of frequency domains,identifies whether there is a non-zero frequency coefficient in eachfrequency domain, generates frequency domain encoding informationindicating whether there is the non-zero frequency coefficient in eachfrequency domain, and encodes the frequency domain encoding information.When the corresponding frequency domain encoding information indicatesthat there is the non-zero frequency coefficient in the frequencydomain, the encoder 150 can scan and encode the quantized frequencycoefficient of the frequency domain. A description of a detailedoperation of the encoder 150 will be made in detail through adescription of an apparatus 200 for subband-coding the frequencyconversion unit according to an embodiment of the present disclosuresince a function of the apparatus 200 for subband-coding the frequencyconversion unit according to the embodiment of the present disclosuredescribed below may be included in a function of the encoder 150.

The inverse quantizer and inverse transformer 160 inversely quantizesand inversely transforms the residual block transformed and quantized bythe transformer and quantizer 140 to reconstruct the residual block. Theinverse quantization and the inverse transform may be achieved byinversely performing the transform process and the quantization processperformed by the transformer and quantizer 140. That is, the inversequantizer and inverse transformer 160 can perform the inversequantization and the inverse transform by inversely performing thetransform and the quantization performed by the transformer andquantizer 140 by using information (for example, information on atransform type and a quantization type) related to the transform and thequantization generated and transmitted from the transformer andquantizer 140.

The adder 170 adds the predicted block predicted by the predictor 110 or120 and the residual block inversely quantized and inversely transformedby the inverse quantizer and inverse transformer 160 to reconstruct thecurrent block.

The frame memory 180 stores the block reconstructed by the adder 170 anduses the stored block as a reference block in order to generate thepredicted block in performing the intra prediction or the interprediction.

FIG. 2 is a block diagram of the apparatus 200 for subband-coding thefrequency conversion unit according to at least one embodiment of thepresent disclosure.

The apparatus 200 for subband-coding the frequency conversion unitincludes a frequency domain splitter 210, a frequency domain encodinginformation generator 220, a frequency domain scan unit 230, and anentropy encoder 240. An encoding stream generator in the apparatus forsubband-coding the frequency conversion unit according to the presentdisclosure may be implemented using the entropy encoder 240. Othercomponents of the apparatus 200, such as the a frequency domain splitter210, the frequency domain encoding information generator 220, thefrequency domain scan unit 230, and the entropy encoder 240 are eachimplemented by one or more processors and/or application-specificintegrated circuits (ASICs).

The frequency domain splitter 210 receives a frequency conversion block,and splits a frequency conversion unit of the received frequencyconversion block into one or more frequency domains.

The frequency domain encoding information generator 220 identifieswhether there is a non-zero frequency coefficient in each of the splitfrequency domains, and generates frequency domain encoding information.

The frequency domain scan unit 230 receives the frequency domainencoding information from the frequency domain encoding informationgenerator 220 and scans a frequency coefficient of each frequency domainto generate a frequency domain frequency coefficient stream.

The entropy encoder 240 binarizes and encodes the frequency domainencoding information and the scanned frequency domain frequencycoefficient stream.

FIGS. 3A to 3F illustrate various examples of splitting the frequencyconversion unit into a plurality of frequency domains, and FIG. 4illustrates numbers of the frequency domains when a 16×16 frequencyconversion unit is split into four 8×8 frequency domains. In FIG. 4,domain 0 corresponds to a low frequency domain, and domain 3 correspondsto a highest frequency domain.

FIG. 3A illustrates four 4×4 frequency domains equally split from an 8×8frequency conversion unit, FIG. 3B illustrates sixteen 4×4 frequencydomains equally split from the 16×16 frequency conversion unit, FIG. 3Cillustrates eight 4×4 frequency domains equally split from an 8×16frequency conversion unit, and FIG. 3D illustrates four 8×8 frequencydomains equally split from a 16×6 frequency conversion unit.

As illustrated in FIG. 3A to 3D, a frequency domain unit by which thefrequency domain splitter 210 splits the frequency conversion unit maybe a 4×4 unit or an 8×8 unit.

Further, as illustrated in FIG. 3E, the frequency conversion unit may besplit into the low frequency domain and one or more remaining domainsexcept for the low frequency domain. In addition, the low frequencydomain may be the left uppermost domain of the frequency conversion unitwhen a length and a width of the frequency conversion unit are equallysplit in half, respectively. For example, FIG. 3E illustrates that the8×8 frequency conversion unit is split into a 4×4 low frequency domainlocated in the left uppermost domain and the remaining frequency domain.

The frequency domain encoding information generator 220 identifieswhether there is the non-zero frequency coefficient in each of the splitfrequency domains. The frequency domain encoding information generator220 generates corresponding frequency domain encoding informationdivisibly for a case where there is no non-zero frequency coefficient inthe frequency domain and a case where there is even a single non-zerofrequency coefficient. For example, the frequency domain encodinginformation generator 220 can generate “0” as frequency domain encodinginformation of the corresponding frequency domain when there is nonon-zero frequency coefficient in the frequency domain, and generate “1”as frequency domain encoding information of the corresponding frequencydomain when there is even a single non-zero frequency coefficient.

The frequency domain scan unit 230 receives the frequency domainencoding information from the frequency domain encoding informationgenerator 220 and scans the frequency coefficient of each frequencydomain to generate the frequency domain frequency coefficient stream.

FIG. 5 illustrates an example schematized from parallel scan operationsof the frequency domain scan unit 230.

As illustrated in FIG. 5, the frequency domain scan unit 230 can scanfrequency coefficients of respective frequency domains in parallel foreach frequency domain. That is, when the frequency conversion unit issplit into four frequency domains as illustrated in FIG. 4, thefrequency domain scan unit 230 independently scans each frequency domainby using a separate scanner, so that the frequency domain scan unit 230can simultaneously perform scan operations of the four domains. As aresult, one domain scanner has only to scan a frequency domain having asize smaller than a size of the frequency conversion unit, and thus thescanner may be more simply implemented. Here, domain 0 of FIG. 4 may bescanned by a first domain scanner 402, domain 1 may be scanned by asecond domain scanner 404, domain 2 may be scanned by a third domainscanner 406, and domain 3 may be scanned by a fourth domain scanner 408in parallel. For reference, the first to fourth scanners 402, 404, 406,and 408 do not fixedly exist within the scan unit 230, and processes forvariably scanning the respective frequency domains according to thenumber of frequency domains may be generated within the frequency domainscan unit 230.

Further, the frequency domain scan unit 230 receives the frequencydomain encoding information and scans only the frequency coefficient ofthe frequency domain having the non-zero frequency coefficient togenerate the frequency domain frequency coefficient stream. That is, thefrequency coefficient of the frequency domain having only the frequencycoefficient which is “0” may not be scanned.

Meanwhile, the frequency domain splitter 210 receives the frequencydomain encoding information from the frequency domain encodinginformation generator 220, and may split again the frequency domain intoone or more sub frequency domains if the frequency domain has thenon-zero frequency coefficient.

For example, the frequency domain splitter 210 can split the frequencyconversion unit into hierarchical frequency domains like a case of the16×16 frequency conversion unit of FIG. 3F. That is, the frequencydomain splitter 210 splits the 16×16 frequency conversion unit into 8×8frequency domains. When the frequency domain splitter 210 receives thefrequency domain encoding information indicating that there is anon-zero frequency in a low frequency 8×8 frequency domain from thefrequency domain encoding information generator 220, the frequencydomain splitter 210 splits the low frequency 8×8 frequency domain intosub frequency domains by splitting the low frequency 8×8 frequencydomain into 4×4 frequency domains, and transmits information on a subfrequency domain division to the frequency domain encoding informationgenerator 220. In this event, the frequency domain encoding informationgenerator 220 identifies again whether there is a non-zero frequencycoefficient in a corresponding sub frequency domain, and generatescorresponding sub frequency domain encoding information divisibly for acase where there is no non-zero frequency coefficient in the subfrequency domain and a case where there is even a single non-zerofrequency coefficient.

The entropy encoder 240 receives the frequency domain encodinginformation from the frequency domain encoding information generator 220and receives the scanned frequency domain frequency coefficient streamfrom the frequency domain scan unit 230 to binarize and encode thefrequency domain encoding information and the scanned frequency domainfrequency coefficient stream.

At this time, the entropy encoder 240 can binarize the frequency domainencoding information into a one bit size having “0” or “1” for eachfrequency domain.

Further, the entropy encoder 240 can encode the frequency domainencoding information with reference to a probability that the frequencydomain encoding information is generated.

Table 1 shows an example of binary information according to thefrequency domain encoding information of each frequency domain of thefrequency conversion unit.

TABLE 1 Frequency Frequency Frequency Frequency Binary Code Domain 0Domain 1 Domain 2 Domain 3 0 0 0 0 0 1111000 0 0 0 1 1111001 0 0 1 01111010 0 0 1 1 1111011 0 1 0 0 1111100 0 1 0 1 1111101 0 1 1 0 11111100 1 1 1 10 1 0 0 0 111000 1 0 0 1 1101 1 0 1 0 111001 1 0 1 1 1100 1 1 00 111010 1 1 0 1 111011 1 1 1 0 1111111 1 1 1 1

Four bit frequency domain encoding information may be encoded by storinga lookup table such as Table 1 based on the probability that there isthe non-zero frequency coefficient in frequency domains 0, 1, 2, and 3illustrated in FIG. 4.

As shown in Table 1, while the number of binary code bits generated whenfrequency domain encoding information of the remaining frequency domainsexcept for domain 0 corresponding to the low frequency domain is all “0”is small, the number of binary code bits generated when frequency domainencoding information of the remaining frequency domains except fordomain 0 corresponding to the low frequency domain is all “1” isrelatively large. The frequency domain encoding information of theremaining frequency domains except for domain 0 corresponding to the lowfrequency domain is likely to be “0”, thereby increasing the totalencoding efficiency.

Meanwhile, since making the lookup table such as Table 1 based on theprobability is already known, its detailed description will be omitted.

FIG. 6 is a schematic block diagram of a configuration of a videodecoding apparatus according to at least one embodiment of the presentdisclosure.

A video decoding apparatus 600 includes a decoder 610, an inversequantizer and inverse transformer 620, a predictor 630 or 640, an adder650, and a frame memory 660. Other components of the video decodingapparatus 600, such as the decoder 610, the inverse quantizer andinverse transformer 620, the predictor 630 or 640, the adder 650 areeach implemented by one or more processors and/or application-specificintegrated circuits (ASICs). The frame memory 660 includes at least onenon-transitory computer readable medium. The video decoding apparatus600 includes input components (e.g., a keyboard, a mic, a touch pad, andso on) and output components (e.g., such as a speaker, a display screen,a printer and so on).

The decoder 610 decodes the encoded data and extracts informationrequired for a block decoding. The decoder 610 can extract the encodedresidual block from the first field included in the encoded data anddecode the extracted residual block, extract information required for aprediction from the second field included in the encoded data, andtransmit the extracted information required for the prediction to theintra predictor 630 or the inter predictor 640.

The decoder 610 receives the encoded data, extracting frequency domainencoding information and a frequency domain frequency coefficientstream, divides a frequency conversion unit into one or more frequencydomains according to the frequency domain encoding information, andinversely scans the corresponding frequency domain frequency coefficientstream according to the frequency domain encoding information and sets aquantization coefficient to reconstruct a transformed and quantizedfrequency conversion block. That is, the decoder 610 can decode theencoded data to extract the frequency domain encoding information, setall quantization frequency coefficients of the corresponding frequencydomain to “0” when the frequency domain encoding information is “0” forthe frequency domain, extract the frequency domain quantizationfrequency coefficient stream from the bitstream (encoded data) when thefrequency domain encoding information is “1”, and inversely scan thefrequency domain quantization frequency coefficient stream throughvarious inverse scanning methods such as an inverse zigzag scan and thelike and set the frequency domain quantization frequency coefficient togenerate the residual block (that is, transformed and quantizedfrequency conversion block) having the quantization frequencycoefficient in every frequency domain.

Here, when the frequency domain has the frequency domain encodinginformation which is “0”, the decoder 610 can set all quantizationcoefficients of the corresponding frequency domain of the frequencyconversion unit to “0” and inversely scan the frequency domain frequencycoefficient stream of the frequency domain where there is the frequencydomain having the frequency domain encoding information which is not “0”to reconstruct the transformed and quantized frequency conversion block(that is, transformed and quantized residual block).

Further, the decoder 610 can extract the frequency domain encodinginformation from the encoded data with reference to the probability thatthe frequency domain encoding information is generated. In this event,the decoder 610 can extract the frequency domain encoding information byusing the same lookup table as the lookup table stored by the encoder150 of the video encoding apparatus 100.

Meanwhile, the decoder 610 can split the frequency conversion unit bythe unit of 4×4 subblocks or 8×8 subblocks in the same way as that ofthe video encoding apparatus 100, and split the frequency conversionunit into the low frequency domain and the remaining domain except forthe low frequency domain. Further, the low frequency domain may be theleft uppermost domain of the frequency conversion unit when a length anda width of the frequency conversion unit are equally split in half,respectively.

Meanwhile, the decoder 610 can inversely scan the frequency domainfrequency coefficient stream in parallel for each frequency domain. Thatis, when the encoder 150 scans the frequency domain frequencycoefficient stream in parallel for each frequency domain, a plurality ofdomain scanners (not shown) may be included within the decoder 610similar to a case where a plurality of domain scanners 402 to 404 areincluded within the encoder 150.

Meanwhile, the decoder 610 decodes the encoded data to decode or extractinformation required for the decoding as well as the transformed andquantized residual block. The information required for the decodingrefers to information required for decoding the encoded bitstream withinthe encoded data. For example, the information may include informationon a block type, information on an intra prediction mode when aprediction mode is the intra prediction mode, and information on themotion vector when the prediction mode is an inter prediction mode,information on a transform and quantization type and the like, but mayinclude various information as well as the above-listed information.

The inverse quantizer and inverse transformer 620 inversely quantizesand inversely transforms the transformed and quantized residual blockwhich is decoded to reconstruct the residual block.

The predictor 630 or 640 predicts the current block to generate thepredicted block. At this time, the corresponding predictor 630 or 640can predict the current block in the same way as that of the predictor110 or 120 of the video encoding apparatus 100.

The adder 650 adds the residual block reconstructed by the inversequantizer and inverse transformer 630 and the predicted block generatedby the predictor 640 to reconstruct the current block. The current blockreconstructed by the adder 650 is transferred to the frame memory 660,and may be used for predicting another block by the predictor 630 or640.

The frame memory 660 stores a reconstructed video to allow an intra andinter prediction block to be generated.

Meanwhile, the video encoding/decoding apparatus according to anembodiment of the present disclosure may be implemented by connecting anencoded data output terminal of the video encoding apparatus 100 of FIG.1 to an encoded data input terminal of the video decoding apparatus 600of FIG. 6.

The video encoding/decoding apparatus according to an embodiment of thepresent disclosure includes a video encoder for predicting the currentblock to generate the predicted block, subtracting the predicted blockfrom the current block to generate the residual block, transforming andquantizing the residual block to generate the frequency conversionblock, splitting the frequency conversion unit of the frequencyconversion block into one or more frequency domains and identifyingwhether there is the non-zero frequency coefficient in each frequencydomain to generate the frequency domain encoding information, scanningthe frequency coefficient of each frequency domain to generate thefrequency domain frequency coefficient stream, and binarizing andencoding the frequency domain encoding information and the scannedfrequency domain frequency coefficient stream; and a video decoder forreceiving the encoded data to extract the frequency domain encodinginformation and the frequency domain frequency coefficient stream,splitting the frequency conversion unit into one or more frequencydomains according to the frequency domain encoding information,inversely scanning the frequency domain frequency coefficient streamaccording to the frequency domain encoding information to set thequantization coefficient, reconstructing the transformed and quantizedfrequency conversion block, inversely quantizing and inverselytransforming the frequency conversion block to reconstruct the residualblock, predicting the current block to generate the predicted block, andadding the reconstructed residual block and the predicted block toreconstruct the current block.

Here, the video encoder may be implemented as the video encodingapparatus 100 according to an embodiment of the present disclosure, andthe video decoder may be implemented as the video decoding apparatus 600according to an embodiment of the present disclosure.

FIG. 7 is a flowchart illustrating a method of subband-coding thefrequency conversion unit according to an embodiment of the presentdisclosure.

The following description will be made with reference to FIGS. 2 to 7.

As illustrated in FIG. 7, the method of subband-coding the frequencyconversion unit according to an embodiment of the present disclosureincludes a block receiving step (S710) of receiving a frequencyconversion block, a frequency domain split step (S720) of splitting afrequency conversion unit of the frequency conversion block into one ormore frequency domains, a step (S730) of identifying whether there is anon-zero frequency coefficient in each frequency domain, a step (S770)of setting frequency domain encoding information to “0” when allfrequency coefficients are “0”, a step (S740) of setting the generatedfrequency domain encoding information to “1” when there is even a singlenon-zero frequency coefficient, a frequency domain scan step (S750) ofreceiving the frequency domain encoding information and scanning thefrequency coefficient of each frequency domain to generate a frequencydomain frequency coefficient stream, and an encoding stream generatingstep (S760) of binarizing and encoding the frequency domain encodinginformation and the scanned frequency domain frequency coefficientstream.

Here, since the block receiving step (S710) and the frequency domainsplit step (S720) correspond to operations of the frequency domainsplitter 210, the step (S730), the step (S740), and the step (S770)correspond to operations of the frequency domain encoding informationgenerator 220, the frequency domain scan step (S750) corresponds to anoperation of the frequency domain scan unit 230, and the encoding streamgenerating step (S760) corresponds to an operation of the entropyencoding unit 240, their detailed descriptions will be omitted.

Meanwhile, referring to FIGS. 1 to 5, a video encoding method accordingto an embodiment of the present disclosure includes a prediction step(S810) of predicting a current block to generate a predicted block, asubtraction step (S820) of subtracting the predicted block from thecurrent block to generate a residual block, a transform and quantizationstep (S830) of transforming and quantizing the residual block togenerate a frequency conversion block, and an encoding step (S840) ofreceiving the frequency conversion block to split a frequency conversionunit of the frequency conversion block into one or more frequencydomains, identifying whether there is a non-zero frequency coefficientin each frequency domain to generate frequency domain encodinginformation, scanning the frequency coefficient of each frequency domainto generate a frequency domain frequency coefficient stream, andbinarizing and encoding the frequency domain encoding information andthe scanned frequency domain frequency coefficient stream.

Here, since the prediction step (S810) corresponds to an operation ofthe predictor 110 or 120, the subtraction step (S820) corresponds to anoperation of the subtractor 130, the transform and quantization step(S830) corresponds to an operation of the transformer and quantizer 140,and the encoding step (S840) corresponds to an operation of the encodingunit 150, their detailed descriptions will be omitted.

Meanwhile, referring to FIGS. 2 to 6, a video decoding method accordingto an embodiment of the present disclosure includes a decoding step(S910) of receiving encoded data to extract the frequency domainencoding information and the frequency domain frequency coefficientstream, splitting the frequency conversion unit into one or morefrequency domains according to the frequency domain encodinginformation, and inversely scanning the frequency domain frequencycoefficient stream according to the frequency domain encodinginformation and setting a quantization coefficient to reconstruct thetransformed and quantized frequency conversion block, an inversequantization and inverse transform step (S920) of inversely quantizingand inversely transforming the frequency conversion block to reconstructthe residual block, a prediction step (S930) of predicting the currentblock to generate the predicted block, and an addition step (S940) ofadding the reconstructed residual block and the predicted block toreconstruct the current block.

Here, since the decoding step (S910) corresponds to an operation of thedecoding unit 610, the inverse quantization and inverse transform step(S920) corresponds to an operation of the inverse quantizer and inversetransformer 620, the prediction step (S930) corresponds to an operationof the predictor 630 or 640, and the addition step (S940) corresponds toan operation of the adder 650, their detailed descriptions will beomitted.

The video encoding/decoding method according to an embodiment of thepresent disclosure may be implemented by combining the video encodingmethod according an embodiment of the present disclosure and the videodecoding method according to an embodiment of the present disclosure.

The video encoding/decoding method according to an embodiment of thepresent disclosure includes a video encoding step (implemented by thevideo encoding method according to an embodiment of the presentdisclosure) of predicting a current block to generate a predicted block,subtracting the predicted block from the current block to generate aresidual block, transforming and quantizing the residual block togenerate a frequency conversion block, and splitting a frequencyconversion unit of the frequency conversion block into one or morefrequency domains, identifying whether there is a non-zero frequencycoefficient in each frequency domain to generate frequency domainencoding information, scanning the frequency coefficient of eachfrequency domain to generate a frequency domain frequency coefficientstream, and binarizing and encoding the frequency domain encodinginformation and the scanned frequency domain frequency coefficientstream, and a video decoding step (implemented by the video decodingmethod according to an embodiment of the present disclosure) ofreceiving encoded data to extract the frequency domain encodinginformation and the frequency domain frequency coefficient stream,splitting the frequency conversion unit into one or more frequencydomains according to the frequency domain encoding information, andinversely scanning the frequency domain frequency coefficient streamaccording to the frequency domain encoding information and setting aquantization coefficient to reconstruct the transformed and quantizedfrequency conversion block, inversely quantizing and inverselytransforming the frequency conversion block to reconstruct the residualblock, predicting the current block to generate the predicted block, andadding the reconstructed residual block and the predicted block toreconstruct the current block.

Here, the video encoding step may be implemented by the video encodingstep according to an embodiment of the present disclosure, and the videodecoding step may be implemented by the video decoding step according toan embodiment of the present disclosure.

In the description above, although all of the components of theembodiments of the present disclosure have been explained as assembledor operatively connected as a unit, the present disclosure is notintended to limit itself to such embodiments. Rather, within theobjective scope of the claimed invention, the respective components maybe selectively and operatively combined in any numbers. Every one of thecomponents is able to be also implemented by itself in hardware whilethe respective ones can be combined in part or as a whole selectivelyand implemented in a computer program having program modules forexecuting functions of the hardware equivalents. Codes or code segmentsto constitute such a program be easily deduced by a person who hasordinary skill in the art. The computer program is stored non-transitorycomputer readable recording medium, which in operation can realize theas some embodiments of the present disclosure. Examples of thenon-transitory computer readable recording medium include magneticrecording media, such as a hard disk, a floppy disk, and a magnetictape, and optical recording media, such as a compact disk read onlymemory (CD-ROM) and a digital video disk (DVD), magneto-optical media,such as a floptical disk, and hardware devices that are speciallyconfigured to store and execute program instructions, such as a ROM, arandom access memory (RAM), and a flash memory.

According to various embodiments of the present disclosure as describedabove, in encoding and decoding a frequency conversion unit of afrequency conversion block, a video compression efficiency is able to beimproved and an implementation is able to be simplified by splitting thefrequency conversion unit into one or more frequency domains, encodingfrequency domain encoding information so that it is indicated whetherthere is a non-zero frequency coefficient in each frequency domain, andencoding the frequency conversion block with reflection of videocharacteristics.

In addition, terms like ‘include’, ‘comprise’, and ‘have’ should beinterpreted in default as inclusive or open rather than exclusive orclosed unless expressly defined to the contrary. All the terms that aretechnical, scientific or otherwise agree with the meanings as understoodby a person of ordinary skill in the art unless defined to the contrary.Common terms as found in dictionaries should be interpreted in thecontext of the related technical writings not too ideally orimpractically unless the present disclosure expressly defines them so.

Although exemplary embodiments of the present disclosure have beendescribed for illustrative purposes, those of ordinary skill in the artwill appreciate that various modifications, additions and substitutionsare possible, without departing from the spirit and scope of the claimedinvention. Specific terms used in this disclosure and drawings are usedfor illustrative purposes and not to be considered as limitations of thepresent disclosure. Therefore, exemplary embodiments of the presentdisclosure have not been described for limiting purposes. Accordingly,the scope of the claimed invention is not to be limited by the aboveembodiments but by the claims and the equivalents thereof.

What is claimed is:
 1. A method performed by an apparatus for decoding avideo, the method comprising: generating a predicted block by predictinga current block to be decoded; reconstructing frequency coefficients ina frequency conversion unit by decoding a bitstream, to generate afrequency conversion block having a size of the frequency conversionunit; inversely transforming the frequency conversion block by using atransform size identical to the size of the frequency conversion unit,to reconstruct a residual block; and adding the reconstructed residualblock to the predicted block, wherein the reconstructing of thefrequency coefficients comprises: identifying a plurality of subblocksin the frequency conversion unit; decoding, from the bitstream,information indicating whether a subblock in the frequency conversionunit has at least one non-zero frequency coefficient; reconstructingfrequency coefficients in the subblock from the bitstream, when theinformation indicates that the subblock has at least one non-zerofrequency coefficient; and setting all frequency coefficients in thesubblock to 0, when the information indicates that the subblock does nothave at least one non-zero frequency coefficient.
 2. The method of claim1, wherein each of the plurality of the subblocks has a size of 4×4pixels.
 3. The method of claim 1, wherein each of the plurality of thesubblocks has a size of 4×4 pixels or 8×8 pixels.
 4. The method of claim1, wherein each of the plurality of subblocks includes frequencycoefficients corresponding to a frequency range, the frequency range ofeach of the plurality of subblocks being different from each other. 5.The method of claim 1, wherein the frequency conversion unit is splitinto a subblock including frequency coefficients corresponding to a lowfrequency range and one or more subblocks including frequencycoefficients except for the low frequency range.
 6. The method of claim1, wherein the plurality of subblocks are reconstructed in parallel. 7.A video decoding apparatus, comprising: a decoder configured toreconstruct frequency coefficients in a frequency conversion unit bydecoding a bitstream, and generate a frequency conversion block having asize of the frequency conversion unit; an inverse transformer configuredto inversely transform the frequency conversion block by using atransform size identical to the size of the frequency conversion unit,to reconstruct a residual block; a predictor configured to generate apredicted block by predicting a current block to be decoded; and anadder configured to add the reconstructed residual block to thepredicted block, wherein the decoder is configured to identify aplurality of subblocks in the frequency conversion unit, decode, fromthe bitstream, information indicating whether a subblock in thefrequency conversion unit has at least one non-zero frequencycoefficient, reconstruct frequency coefficients in the subblock from thebitstream, when the information indicates that the subblock has at leastone non-zero frequency coefficient, and set all frequency coefficientsin the subblock to 0, when the information indicates that the subblockdoes not have at least one non-zero frequency coefficient.
 8. Theapparatus of claim 7, wherein each of the plurality of the subblocks hasa size of 4×4 pixels.
 9. The apparatus of claim 7, wherein each of theplurality of the subblocks has a size of 4×4 pixels or 8×8 pixels. 10.The apparatus of claim 7, wherein each of the plurality of subblocksincludes frequency coefficients corresponding to a frequency range, thefrequency range of each of the plurality of subblocks being differentfrom each other.
 11. The apparatus of claim 7, wherein the decoder isconfigured to split the frequency conversion unit into a subblockincluding frequency coefficients corresponding to a low frequency rangeand one or more subblocks including frequency coefficients except forthe low frequency range.
 12. The apparatus of claim 7, wherein thedecoder is configured to reconstruct the plurality of subblocks inparallel.